The field of the disclosure relates generally to the detection of objects using resonant radio frequency location, and more specifically, to methods and systems for determining the phase constant of a dielectric medium within which such objects could be embedded.
The detection and identification of an object using resonant radio frequency (RF) location generally requires prior knowledge of the spectral response of the object to incident RF energy. However, when the object is embedded in a medium other than air, such as an object embedded in sand or other medium, the spectral response of the object, and thus its resonant frequencies, are shifted by a factor equal to 2π multiplied by frequency and divided by the phase constant of the medium and the wavelengths of the spectral components. The phase constant is a factor dependent upon frequency and the permeability/permittivity of the medium. Without knowledge of either the permeability/permittivity or the phase constant of the medium, the reflected spectral response, including the resonant frequencies, of a buried object cannot reliably be predicted, and resonant RF location cannot be effectively used to detect and identify the object.
The permeability, permittivity, and phase constant typically cannot be measured without access to a sample of the medium. Furthermore, the dielectric properties of certain media vary with conditions such as bulk density, water content, and composition. Thus, a permeability, permittivity, or phase constant measurement taken at one time cannot be used reliably to determine the spectral response of an embedded object at another time.
In the application of resonant RF location to cases like the detection of objects buried in a medium, such as sand, with unknown dielectric properties a method is needed for remotely and immediately determining the permeability and permittivity or phase constant of the medium.